Infinite stage pump



June 7, :1949.l D. GRANT Em. 2,472,104

INFINITE STAGE PUMP Filed Jan. 3, 1947 JNVENTORS. /v/cHoL/ia BRJHHBK DHV/D G/ HND Patented June 7, 1949 l OFFICE INFINI'IE- STAGE PUMP David Grant, Los Angeles, Calif., and Nicholas Bashark, Dayton, Ohio Application January 3,' 1947, Serial No. 719,974

(Granted under the act of March 3, 1883, as

1 Claim.

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to us of any royalty thereon.

This invention relates to hydraulic pumps, and particularly to mechanism for eiecting infinitesimal variation of pressure and volume in inverse I ratio.

An object of the invention is to provide a hydraulic pump whereby a relatively uniform power input stroke will deliver a progressively decreasing volume at a proportionately increasing pressure.

Another object of the invention is to provide a pump of this character with operating leverage, the mechanical advantage of which increases by iminitesimal increment as the volume required diminishes and the pressure required increases.

In the master cylinder of a hydraulic brake system, braking is accomplished by actuating the master piston through a single stroke, and in such a system it would be highly advantageous if, during the rst part of its stroke, the master piston would deliver a relatively large volume of uid at a low pressure and thereafter progressively decrease Athe volume and correspondingly increase the pressure throughout the remainder of the stroke without, however, increasing the actuating effort.

It is therefore another object of this invention to provide a mechanism of this character in which the master cylinder on the discharge side of the master piston is connected td a hydraulically operative device for increasing the mechanical advantage of the actuating pedal as the pressure toward the end of the stroke becomes greater and the volume of fluid required becomes less.

Other objects, advantages and meritorious features will become evident as the invention isI described in detail with reference to the drawings, wherein,

Fig. 1 is an axial section taken at I-I of `Iliig. 2 through a pump suitable for actuating a hydraulic ram orv similar device and made in accordance with my invention.-

Fig. 2 is an axial section taken at 2-2of l Flg.`1.

Fig. 3 is an axial section through a master brake'cylinder and piston equipped with an embodiment of my invention.

Fig. 4 shows an antifriction bearing which may be employed in my mechanism.

Like reference characters refer to like pan throughout the several views.

Referring more particularly to Fig. l, a pum '1 cylinder I Il with piston head I2, lpiston rod It suction intake valve I 6, and discharge valve I is of substantially conventional design, iiul entering at and being'discharged at 22. Th piston I2 and rod I4 are providedrcspetivel with packings 24 and 26. The suction intali, valve I6 and the discharge valve I8 are provide respectively with closing springs 28 and 30. Fc purposes of description, the piston head I2 an piston rod I4 may collectively be referred to a the piston I5. i

An auxiliary cylinder 32 is carried on the pum; cylinder I0, the axes of the two cylinders being f substantially normal one to the other. A bracket 34 joins the two cylinders I Il and32 to maintain them vin xed relation.

Auxiliary cylinder 32 is slidably fitted with a piston head 36 having a piston rod 38 which has sliding bearing in a plug 40 which is in threaded engagement with the cylinder at 42. A compression spring 44 is interposed between the piston 36 and nut l4I), the stress of the spring 44 being adjustable by means of the nut 40. A vent 45 is provided to allow air to escape from the spring chamber. A slot '43 is provided in the nut 40 for adjustment thereof. A packing 48 is provided for the piston head 36. For purposes of description the piston head 36 and the piston rod 38 may collectively be'referred to as the piston 4I. The discharge space 35, to the right of the piston I2 in the main cylinder I0 is connected to the space 31 under the piston 36 in auxiliary cylinder32 by a passageway 39.

The outer ends of the main piston rod I4 and the auxiliary pistn rod 38 are respectively forked as at 50 and 52 (see Fig. 2), and between the prongs of the forks lies a hand lever 54. The lower end of the hand lever 54 is hinged to the upper end of the piston rod 38 by a pin 56. A second pin 58 carried in the prongs of the fork 50 passes through a slot 60 in the hand lever 54. Obviously the raising or lowering of the piston rod 33 changes the ratioof the power arm X to the work arm Y of the hand lever 54.

Assuming for illustrative purposes only, that thel pump shown in Figs. 1 and 2 is about-to be used for operating a hydraulic jack which is to lraise a relatively heavy weight, and that the top 3 of the jack ram happens to be somewhat below the weight which is to be lifted.

When pumping starts, the auxiliary piston 38 will be all the way down and the top of the slot 50 will be resting on the pin 58. Since, at the beginning, the weight of the jack ram only is to be lifted, the auxiliary piston 88 may remain at the bottom until the top of the jack ram encounters the weight.

As the slack begins to be taken up, however, the resistance, and consequently the discharge pressure, in the space 35 of the pump increases gradually, and is transmitted through the passageway 39 to the space 31 which raises the auxiliary piston 36 against the resistance of the spring 44. thereby altering the ratio of X to Y, whereby the .stroke of the upper end of the hand lever 54 and the force necessary to'be applied thereto remains substantially the same whether pumping a large volume against a lowpressure or a smaller volume against a higher pressure.

The exempliflcation shown in Fig. 3 is particularly applicable to a hydraulic brake. includes a master cylinder 82, piston 84, piston rod 86, and brake fluid supply tank 88 with port 10 connecting the tank and cylinder. The piston rod 68 is.slidab1y fitted to a nut 12 which is in threaded engagement with the cylinder 62 and is slotted at 14 for a wrench. A vent 15 is provided for allowing air to escape from between the piston 64 and nut 12. A spring 16 lies between the left end of the piston 64 and the end of the cylinder 62 urging the piston rightwise. An

` outlet port 18 is provided for uid connection to the brakes or other device being operated. Packings 80 seal the piston 84 against leakage.

The auxiliary cylinder 82, substantially like that shown in Fig. 1 is carried on the master cylinder 62, the axes of the master and auxiliary cylinders being at right angles one to the other. A bracket 84 joins the cylinder 82 and 82 in fixed relation.

Auxiliary cylinder 82 is fitted with a sliding piston 88 havinga piston rod 88 which has sliding bearing in a plug 90 which is screwed into the cylinder 82 by means of a suitable wrench which may be tted to the slot 92. A compression spring 94 urges the piston 86 downward, the stress in the compression spring being adjustable by means of the nut 90. A vent 95 allows air to escape from the spring chamber. A packing ring 98 seals the piston 86 against leakage. i The discharge space 98 to the left of piston 64 is connected to the space I under the piston 86 by a passageway |02.

The outer ends of the main and auxiliary piston rods 88 and 88 are respectively forked at |04 and |08, a foot pedal |08 lying between the prongs of the forks. The lower end of the foot pedal |08 is hinged to the upper end of the` piston rod 88 by a pin I0. A second pin I2 carried in the prongs of the fork |04 passes through a slot |`|4 in the foot pedal |08. Raising or lowering of the piston rod 88 changes the ratio of the power arm X' to the work arm Y of the foot pedal |88.- The brake actuating mechanism of Fig. 3 operates substantially like the pump described with reference to Fig. l except that a complete brake actuation is accomplished by a single stroke of the foot pedal |08.

When a brake actuation starts, the first portion of the stroke is used in bringing the braking sur..

faces into engagement which obviously requires little force applied to the pedal |08. The auxiliary piston 86 will therefore be at the bottom of the space |00 and the top of the slot H4 will be resting on the pin ||2.

After the braking surfaces have been brought into contact, however, the pressure will be further increased but preferably somewhat gradually so that deceleration may be not too rapid. Now in conventional braking devices this pressure would be increased wholly by increasing the foot pressure on the pedal |08, while in the Ibraking device of Fig. 3, substantially the same pressure on the foot pedal |08 throughout its stroke will gradually increase the pressure on the braking surfaces to a ,high value because of the transfer of fluid under pressure through the passageway |02 which raises the auxiliary piston 88, thereby gradually changing the ratio of the power arm X to the work arm Y.

Fig. 4 illustrates a means of reducing the bearing friction on slot 60 of the hand lever 54 or slot |14 of the foot pedal |08. Here a fitting ||8 is placed over a pin 5 and a slot I9 is made somewhat larger as at ||8. The fitting is provided with needle bearings ||1 on the surfaces that mate with the faces I8 of the slot I9. The contact area of iitting ||8 is itself relatively large which reduces the unit pressure. This coupled with the use of the needle bearings reduces frictipn and wear.

Devices made in accordance with this invention have many advantages. A pump which includes this invention will have a high volumetric the operating lever is more simple than in any multi-stage pumps heretofore known.

The invention is readily applicable to hydraulic brakes and the like, an example of which is seen in Fig. 3. Since the greater portion of the total operating cycle is at Very low pressure and consequent high volume, much of the operating stroke of the pedal remains for applying the re maining small volume at very high pressure, and this without increasing the foot pressure on the pedal as is required in brake systems of common practice.

Inasmuch as a braking unit as seen in Fig. 3 automatically adiusts itself to an X/Y position which is commensurate with the need in anyv case, it follows that the same unit may be used for a wide variety of applications without adjustment.

Having described several embodiments of our invention, we claim:

In a device of the character described, a main cylinder, a main piston slidable axially in said main cylinder dividing said main cylinder into suction and discharge chambers, an auxiliary cylinder, an auxiliary piston slidable axially in said auxiliary cylinder, theaxes of said cylinders being substantially at right angles to each other, a lever of the second class, a guide slot in said lever intermediate the ends of said lever extending lengthwise thereof, load transmitting means hinged on the outer end of said main piston slidably fitted to said slot, whereby said lever isslidable .bodily endwise along said load transmitting REFERENCES CITED means, a fulcrum means connecting the end of v said lever to the outer end of said auxiliary pislgtef ilgvggerferens are of record in the ton, wherey said lever may be moved bodily by said Yauxiliary piston toward or away from the 5 UNITED STATES PATENTS axis of said main piston, spring means urging Number Name Date said auxiliary piston axially away from the axis 4 1,649,356 Louis Nom-15, 1927 of said main cylinder, and a passageway connect- 1,813,073 Nyrap July '1, 1931 ing the high pressure side of said main piston 1,324,467 Darby et a1 sep1; 22, 1931 to the inner end of said auxiliary piston. .10 y

DAVID GRANT.

NICHOLAS BASHARK. 

